There has been considerable research on the physiological mechanisms of fusion and stereopsis of animals, but there is very little behavioral data on the binocular vision of these same animals. The research is directed toward a behavioral investigation of the binocular vision of the rhesus monkey (Macaca mulatta). In this research, depth discrimination procedure will be used in all binocular vision investigations. Two measures of binocular vision will be investigated. 1) Stereopsis, using computer generated random dot stereograms as a visual stimulus. Stereoacuity for stimuli with both crossed and uncrossed disparity will be determined. 2) Fusional amplitudes, using the procedure of forced vergences in which the vergence demand for single binocular vision is changed until a compensating fusional reflex fails to occur. In each phase of the investigation the monkey data will be directly compared to data from human subjects with normal, single binocular vision and collected using the same apparatus as used for the animal research.